This invention relates to a method for producing a harness of a connector for connecting between electric appliances and the like and a mold for use in the method, and more particularly to an improved method for holding wires in producing a harness of a connector.
A hitherto used method for producing a harness of an electrical connector by the use of the insert-molding will be explained by referring to FIG. 3A illustrating a harness 50 of the prior art in a perspective view, FIG. 3B illustrating a mold in section during insert-molding, FIG. 4A showing a harness having a defect in a perspective view, and FIG. 4B illustrating a mold in section causing such a defect in the harness.
The term xe2x80x9charnessxe2x80x9d used herein is to be understood as an assembly of contacts, wires or the like aligned in a unit with the aid of an insulator in order to facilitate to operate them.
The term xe2x80x9cinsert-moldingxe2x80x9d is one molding method in that after members have been arranged in a mold, a molten material is poured into the mold to obtain a unitarily molded article having the members embedded therein.
The harness 50 mainly consists of an electrical insulator 52, metallic contacts 14 and wires 16. The wires 16 are connected to the respective contacts 14 by means of solderless joining or piercing. A desired number of the contacts 14 connected to the wires 16 are fixed in the electrical insulator 52 by means of the insert-molding.
Materials for the insulator 52 are required to have a good flowability when being poured into a mold, and examples of such materials include liquid crystal polymer (LCP), polyamide (PA66) and the like. The liquid crystal polymer (LCP) is preferable in consideration of heat resistance and moldability.
The insert-molding for molding the harness 50 will be explained by referring to FIG. 3B. The illustrated mold consists of an upper mold 18 and a lower mold 20. The upper mold 18 has a resin pouring inlet 30 as shown in dash-dot lines in FIG. 3B for pouring a resin into a cavity of the upper and lower molds after these molds have been clamped. Each of the upper mold 18 and the lower mold 20 may be of a one-piece mold structure, but molds separable along the broken lines may be preferable because of ease in fabrication.
In molding, the contacts 14 connected to the wires 16 are set in predetermined positions in the lower mold 20. The upper mold 18 is then put on the lower mold 20, and the upper and lower molds 18 and 20 are clamped. On being clamped, the contacts 14 and the wires 16 are securely restrained respectively by contact restraining portions 24 and wire restraining portions 40 formed in the upper and lower molds to avoid any possible leakage of a molten resin. A clearance between the contacts and the contact restraining portions is of the order of 0.02 mm in order to prevent the contacts from being damaged and to avoid the leakage of the resin.
Thereafter, a molding resin is poured through the resin pouring inlet 30 into the cavity. After solidification of the resin, the molds are opened and the harness 50 is manually or automatically removed therefrom.
In the insert-molding of the prior art described above, in general, a tensile force has been applied to the wires during the insert-molding, in order to prevent the wires from slacking or bending because in the cavity the wires 16 are longer than the contact 14. On the other hand, however, a compressive force has been applied from the wire 16 onto the contact 14 in the direction shown by an arrow C in FIG. 4B, in order to position the distal ends of the contacts 14 with high accuracy or to align the distal ends of the contacts 14 in a straight line perpendicular to the longitudinal axes of the contacts 14.
In such a procedure, as in the cavity the wires 16 are usually longer and more flexible than the contacts, the wire 16 would often be deformed or bent upon being subjected to the compressive force as shown in FIG. 4B or subjected to the pressure of the molding resin poured into the cavity. As a result, part of the coating of the wire 16 exposes at the surface of the insulator 52 as shown at reference numeral 44 in FIG. 4A, which is a problem to be solved. Such a harness with an exposed wire could not be used and would be discarded, resulting into increased cost of fabrication.
It is an object of the invention to provide an improved method for producing a harness and an improved mold for use in the method, capable of easily and accurately positioning the distal ends of contacts without exposing part or parts of wires at the surface of the harness.
In order to accomplish the above object, in the method for producing a harness of a connector in a mold by the insert-molding, said harness composed of contacts, wires connected to said contacts and an insulator for holding and fixing therein said contacts connected to said wires, said mold consisting of an upper mold and a lower mold, these upper and lower molds having contact restraining means and wire restraining means for restraining said contacts and said wires in predetermined positions, said method including steps of arranging said contacts connected to said wires in predetermined positions in said lower mold, putting said upper mold on said lower mold and clamping said upper and lower molds, pouring a plastic material into said molds, cooling or heating said plastic material for a predetermined time so as to be solidified or hardened, and removing the solidified or hardened plastic material together with said contacts and wires from said upper and lower molds, according to the invention said upper and lower molds are provided with upper mold holding means and lower mold holding means, respectively, which are located at wire restraining positions of said upper and lower molds and extend into the cavity of said upper and lower molds, and said upper and lower molds are further provided with elastic means arranged to urge said upper and lower holding means in a manner such that said upper and lower mold holding means extend into said cavity of said upper and lower molds to hold said wires before pouring said plastic material into said cavity, but said upper and lower holding means are forced out of the plastic material by its pressure when it is being poured into said cavity of said molds.
Further, the mold for use in the method for producing a harness according to the invention is characterized in that said mold comprises a lower mold having contact restraining means and wire restraining means, and an upper mold to be fitted with said lower mold and having contact restraining means and wire restraining means similarly to said lower mold and further having contact positioning means, and in that said upper mold and said lower mold are provided with upper mold holding means and lower mold holding means, respectively, these upper and lower mold holding means extending into the cavity of said upper and lower molds at opposite positions for restraining said wires, and said upper mold and said lower mold are further provided with elastic means arranged to urge said upper and lower mold holding means into said cavity of said upper and lower molds.
The invention having the subject matters described above can bring about the following significant effects.
The upper and lower mold holding means or members securely hold the wires by the instant when the molten plastic material starts to be poured into the cavity of the upper and lower molds, so that the wires are not bent and not exposed at the surface of the insulator even if they are subjected to the compressive force in their axial directions or subjected to the pressure of the molten plastic material.
The elastic means such as compression springs are arranged to urge the upper mold holding means and the lower mold holding means in a manner such that the upper and lower mold holding means securely hold the wires before pouring the molten plastic material but are forced out of the insulator by the pressure of the molten plastic material being poured into the cavity of the upper and lower molds, thereby obtaining a harness of a connector free from defects.
The mold according to the invention comprises the positioning means, against which the distal ends of contacts can be brought into abutment by applying compressive force to the wires, thereby facilitating the positioning of the contacts.
The invention will be more fully understood by referring to the following detailed specification and claims taken in connection with the appended drawings.